This invention relates generally to optical disk media and more specifically to attachment of adhesive backed rings used for write protection on rewritable compact disk media and similar optical disk media.
Rewritable mass memory media is typically contained in a rigid protective cartridge during operation and the cartridge typically includes a write-protect feature to protect information on a storage medium from being destroyed. For example, many data tape cartridges have a moveable plastic tab on the cartridge that can be moved to one of two positions. Similarly, flexible diskettes in hard plastic cases have a sliding or breakaway plastic tab on the plastic case. Rewritable compact disks (CD-RW) and rewritable Digital Versatile Disks (DVD, also called Digital Video Disks), however, are not in a cartridge during operation. Compact discs are commonly stored in clear plastic containers commonly called xe2x80x9cjewelxe2x80x9d cases or jewel boxes, but the disks are removed from these boxes during operation. Therefore, write protection for CD""s and DVD""s must be implemented directly on the disk medium. Solutions have been proposed that are software based. That is, if a particular bit or data field has a particular value, software (operating system or drive controller) is not supposed to overwrite data on the medium. However, software solutions require support by all operating systems, software drivers and drives. If a disk is created by one operating system or drive controller that supports a software write-protect feature, and then is taken to a system that does not support the feature, data may be inadvertently destroyed. In addition, a software virus could bypass software write protection to delete data on the disk. There is a need for a physical write-protect feature, directly on the disk medium, that protects against writing for any software or any drive.
Industry standard CD-RW media use a phase change material having a transparency that can be reversibly changed by heating, and then cooling at a controlled rate. In CD-RW drives, a laser is used to heat, and then cool small areas at a controlled rate. Laser power must be calibrated for each disk medium. Before writing or erasing, a standard CD-RW drive must successfully calibrate laser power by writing into a Power Calibration Area on the medium. If the drive cannot read the calibration patterns in the Power Calibration Area, it will not erase or write in the data area of the disk. U.S. application Ser. No. 08/823,823, hereby incorporated by reference, discloses a write-protect device in which the Power Calibration Area is covered by a removable opaque adhesive backed ring. Optical disks of interest have a central hole. Drives grip the optical disk around the central hole using mechanisms that may be sensitive to the thickness of the optical disk. Therefore, the write protect ring preferably does not intrude in the area of the disk immediately surrounding the central hole in the disk. The permissible mechanical tolerance for positioning a write-protect ring is relatively small. However, if a write-protect ring cannot intrude into the area adjacent to the central hole in the disk, the central hole in the disk cannot be used to directly align a write-protect ring. There is a need for a low cost, easy-to-use system for precise positioning of adhesive backed write-protect rings onto optical disks. U.S. application Ser. No. 08/932,849, filed Sep. 18, 1997, hereby incorporated by reference, offers one such system. The present application offers another such system.
A write-protect ring is formed from a multilayer material. The material comprises an adhesive backed label layer and a backing layer. When installed on an optical disk, the write protect ring covers the area necessary to prevent writing to the disk. In operation, the backing layer is removed from the write-protect ring, exposing the adhesive, and the write-protect ring is pressed against the data side of the disk. The write-protect ring is left attached to the disk.
The first example embodiment of the invention provides a device that positions the write-protect ring so that it is aligned with the center hole of the disk. Aligning the write-protect ring with the center of the disk ensures that the ring is in the correct location, thereby enabling the write protect function. The device includes a hub upon which the center hole of the disk is pressed, thereby securing the disk to the device. The device also includes a support that surrounds the hub and is connected to the hub so that it may move axially along the hub. This support serves as a shelf for the write-protect ring and a press to assure good contact between the disk and the adhesive of the write-protect ring.
In operation the write-protect ring is positioned on the support with the adhesive exposed and facing upwards away from the support. The disk is then placed on the hub with its data side down. As the hole of the disk is pressed down upon the hub, the support of the device presses the write-protect ring against the disk, causing the write-protect ring to adhere to the disk. The disk is then removed from the device and it is now write-protected by the write-protect ring that is adhered to its data side.
The write-protect ring may also include a removable ring shaped alignment area. The alignment area is surrounded by the write-protect ring and forms a hole in its center that has the same diameter as the central hole of the disk. The alignment area helps the device of the present invention ensure that the write-protect ring is aligned to the center of the hole in the disk. After the disk with the write-protect ring attached is removed from the device, the alignment area is removed, leaving just the write-protect ring attached to the disk.
Multiple write-protect rings may be provided as tear-away features in an insert for the cover of the jewel case. Write-protect rings may be removable. Alternatively, if desired, permanent write-protect rings may be implemented by using a material with an adhesive that is extremely difficult to remove without damaging the disk.